Example embodiments of the inventive concept relate to a piezoelectric composite and an ultrasonic apparatus with the same, and in particular, to a charging device with a piezoelectric composite and an ultrasonic apparatus with the same.
An ultrasonic apparatus is realized using a ceramic/polymer composite. A lead-zirconate-titanate (PZT) based piezoelectric material exhibits an excellent piezoelectric property at each vibration mode (e.g., d33˜510 pC/N and d31˜−230 pC/N) but exhibits a disadvantage of small hydrostatic pressure piezoelectric property (dh).
Generally, the PZT has a small hydrostatic pressure piezoelectric property (dh=d33+2d31) of about 50 pC/N, and thus, to increase dh of the ultrasonic apparatus, d31, transversal vibration mode, is decreased and d33, a vibration mode in a thickness direction, is constantly preserved. In addition, since the pure PZT has a very high density, in-water impedance thereof is very different from that of water. This leads to a problem in transceiving operations of the ultrasonic apparatus. For example, if a sonic wave is incident from a low density medium (e.g., water) to a high density medium (e.g., ceramics), a dense medium does not absorb and reflect the sonic wave, and thus, the reception ratio is decreased. A ceramics-polymer piezoelectric composite has been developed as the one of alternatives to the PZT based piezoelectric material.
The piezoelectric composite can be classified into ten types (e.g., 1-3, 2-2, 0-3, 3-3, and so forth) according to its vibration mode, where the front number is a dimension of ceramics and the rear number is a dimension of epoxy. For example, 1-3 mode piezoelectric composite describes a three-dimensional polymer matrix and one-dimensional piezoelectric fiber inserted therein, and 2-2 mode piezoelectric composite describes a plate-shaped piezoelectric material inserted into a plate-shaped polymer. The most typical type of the ceramics-polymer composite is a 1-3 mode ceramics-polymer piezoelectric composite. In this case, d33 can be maintained constantly by arranging the piezoelectric composite along a specific direction, and d31 mode is suppressed by separating the piezoelectric fibers from each other. Accordingly, dh can be increased. Since the polymer has a low density, the total impedance can be greatly reduced. Accordingly, it is possible to achieve an impedance matching between water and the piezoelectric composite, and an operation of transceiving a sonic wave can be executed with an increased efficiency.
In the meantime, a lithium ion battery and a lithium polymer battery are two typical examples of lithium secondary battery. The lithium ion battery includes an electrolyte layer and an isolation layer, but it suffers from instability, limitations in shape and capacity, and a difficulty of fabrication process. The lithium polymer battery includes a polymer electrolyte serving as both of the electrolyte and isolation layers, thereby overcoming the technical problems of the lithium ion battery. Recently, a research on a monomer electrolyte layer is being conducted.
The polymer electrolyte can be classified into solid-type and gel-type, depending on whether it contains an organic electrolyte or not. The solid-type polymer electrolyte suffers from low ion conductivity and bad mechanical property, and thus, the gel-type polymer electrolyte has been researched for commercialization.